﻿<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            margin: 200px;
        }
        span{
            display: inline-block;
            width: 40px;
            height: 40px;
            background-color: #333;
            font-size: 20px;
            color: #fff;
            text-align: center;
            line-height: 40px;
        }
    </style>
</head>
<body>
    <div>
    <span class="hour">1</span>
    <span class="minute">2</span>
    <span class="second">3</span>
    </div>
    <script>
        //1.获取元素
        var hour = document.querySelector('.hour');//小时的黑色盒子
        var minute=document.querySelector('.minute')//分钟的黑色盒子
        var second =document.querySelector('.second')//秒数的黑色盒子
        var inputTime = +new Date('2027-9-5 23:33:00')//返回用户输入时间总的毫秒数
        countDown();//先调用一次函数，防止第一次刷新页面有空白
        //2.开启定时器
        setInterval(countDown,1000);
        function countDown(){
            var nowTime = +new Date();//返回的是当前时间总的毫秒数
            var times = (inputTime - nowTime) / 1000; // times是剩余时间总的秒数 
            var h = parseInt(times / 60 / 60 % 24); //时
            h = h < 10 ? '0' + h : h;
            hour.innerHTML = h; // 把剩余的小时给 小时黑色盒子
            var m = parseInt(times / 60 % 60); // 分
            m = m < 10 ? '0' + m : m;
            minute.innerHTML = m;
            var s = parseInt(times % 60); // 当前的秒
            s = s < 10 ? '0' + s : s;
            second.innerHTML = s;
        }

        
    </script>
</body>
</html>